Swivel base



FIG. 1 is a perspective view, according to the present invention;

FIG. 2 is a top-side elevational view thereof;

FIG. 3 is a right side elevational view thereof, with a left side elevational view, a front elevational view, and a back elevational view thereof being identical to the right side elevational view; and,

FIG. 4 is a bottom elevational view thereof.

The broken lines shown in the drawing are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a swivel base, as shown and described. 